The present invention relates to auto-adhesive display films comprising at least one electrically charged layer, which are adapted to automatically adhere to most smooth surfaces such as window panes, walls, boards or the like.
From among these display films, the invention relates more specifically to those which comprise at least a first dielectric layer, said layer comprising, on the one hand, a first surface and, on the other hand, a second electrically charged surface.
Display films of this kind that are currently known generally comprise a layer constituted of a polymer material, preferably polypropylene. As a result of the electrostatic force created by the presence of electric charges which are contained inside this layer, it is possible to instantly adhere the display films to most smooth surfaces.
A drawback of these display films, however, is that the surface of the support layer which is not in contact with the smooth surface has the tendency to attract various particles such as dust, smoke etc . . . , present in the surrounding air. As a consequence, the visual aspect of these supports deteriorates rapidly. Furthermore, these particles may be ionised or may carry electric charges, causing the electrostatic force which adheres the, display support to said smooth surface to be reduced.
A particular aim of the present invention is to remedy those drawbacks.
To this end, display films of the kind in question are characterized in that a first screen layer, adapted to form a barrier to the electric field, is fixed to at least, the said first surface, of the first dielectric layer.
In preferred embodiments of the invention, use is also made of one or more of the following dispositions:
the material constituting the first dielectric layer is selected from a polypropylene and a polyethylene terephtalate;
the material constituting the first dielectric layer is a polymer comprising at least one atom of fluorine per monomer;
the polymer is selected from polytetrafluoroethylene and polyfluoroethylenepropylene;
the first screen layer is constituted of a material with a conductivity equal to at least 10xe2x88x9210 S/cm;
the material constituting the first screen layer is a metal;
the material constituting the first screen layer comprises at least one transparent and conductive, metallic oxide;
the first dielectric layer and the first screen layer are transparent;
the first screen layer is permanently fixed to the first dielectric layer;
a removable cover foil is fixed to the second surface of said first dielectric layer, this cover foil comprising at least one second screen layer; this is advantageous in that the display support may be packed into a ream and be used sheet by sheet in a press or a printer, without the stacked supports sticking to one another, like they would in known auto-adhesive display supports;
the second screen layer is substantially identical to the first screen layer;
the cover foil comprises at least a second dielectric layer which is fixed to the second screen layer and placed between this second screen layer and the first dielectric layer;
the material constituting the second dielectric layer is a polymer;
the first and second dielectric layers are constituted of the same material;
the first and second dielectric layers have substantially the same thickness;
the second screen layer is permanently fixed to the second dielectric layer;
the first screen layer is continuous.